Telephone-exchange



` retical diagram so much of my improved telephone-exchange asis necessary to illustrate the led June 12, 1880.

UNITED STATES PATENT OFFICE,

HORACE HAivrLiNE ELDEED, OEBOSTON, MASSACHUSETTS, ASSIGNOE To THEWESTEEN ELECTRIC COMPANY, OE CHTCACQILLTNOIS.

EXCHANGE.

SPECIPICATION forming part of Letters Patent No. 382,518, dated May 8, 1888.

Application niermann 7, reel.`

To all whom it may concern.-

Be it known that I, HORACE HAMLINE EL- DRED,a citizen of the United States, formerly a resident of New York city, but now residing in Boston, Massachusetts, have invented a new l and useful Improvement in Telephone'Exchanges, of which the following is a specification.

My invention relates to an organization of electric circuits and apparatus, usually termed a district telephone or exchange system,` which consists of a number of separatelines or circuits .eaeh of which isso'arranged as to connect one or more subscribers7 instruments, hereinafter termed sub-stations, 7" directly with a district exchange or connecting-office. This arrangement enables any substation in the system to be placed in direct telep/honic connection with any other sub-station in the same system through theexchangeofce by making the necessary circuit connections at the latter point. The organization and operation of such a system are clearly shown and described in my application Serial No. 11,759,

The subject-matter herein l claimed consists in the combination, as hereinafter set forth,v of a series of subscribers lines converg` ing to a common switch-board, switch apparatus adapted for temporarily connecting any two of said lines, switching and calling mechanism mounted on an operators table and in a loop connected with said switching mechanism, and indicators to notify the tableoperator of connections made on the switchboard with the loop-lines on the table.

The accompanying drawing shows in theoinvention herein claimed.

I have shown, yin illust-ration of my inven-A tion, a centralexchange station having nine independent lines radiating therefrom, which extend to or connect with -a likeV number of different sub stations. The apparatus at the several sub-stations is constructed and arranged :in a well-known manner, and consists of apparatus for transmitting and receiving calls and signals and a transmitting and reserialrro. 123.381. No model.)

ceivingtelephone with the necessary switches, 5o which telephones may be separate, or combined in one instrument, as found :most con-y venient in any particular case. The apparatus at each sub -station is connected in the usual manner with the earth and also by means of a line-wire with the central station,

as hereinbefore stated. In the drawing' these different sub-station lines are seen entering the switch S at the central station, and are designated, respectively, by numbers, as 1, ,2, 3, 4, 6o 5, 6, 7, 8, 9, and 10. The switch-board S is i provided with a series of spring-jacks, J J2, &c one to each sub-station line, the construction of which is well known, and therefore re- Y quires no special description. jack normally presses firmly against a separate insulated metallic plate, as shown at c e e, each of which plates is connected by a wire (shown by a dotted line) to a corresponding annunciator or visual electro-magnetic signal 7o or annunciator, A YA3, C. After passing through these all the wires are joined together and connected with aconimon Wire, g, leading to the earth at G.

The means which 1 preferito employ for 75" n coupling or connecting the different. lines to! gether in pairs for direct communicationl 'are similar to those described ina pending application filed by me on orv about the 9th dayof v J u ne,"1880, Serial N o. 11,389, patented Aug-ust 8.o 19, 1884, as No. 303,714, and are as follows:

A exible insulated conductor, O, is'provided'YV with a wedge-shaped terminal, N, at one ex! tremity, which terminal has one conductingface, n, and one non-'conducting face, n. The.,85 construction of this terminal andthe manner in which it is designed tok be inserted into the spring-jack are well known. It may be re-v marked, however, by way of explanation Vthat when the terminal N is insertedinto aspring- 93 jack, with its conducting-face n uppermost, the previously #existing connection between Athe Y line-wire and the annunciator and earth is interrupted, and the line-wire is at the sam'e time placed in connection through the Conf 95 Y ducting-face n of the terminal N with the conductor O. If the terminal N be withdrawn 'from the spring-jack, the line is automatically Each spring- 65 restored to its normal connection with the annunciator and the earth. The opposite extremity of the flexible conducting-cord O terminates in a tapering metallic peg, P, which is adapted to be inserted with a twisting motion into one of a number of suitableholes provided for that purpose in thehorizontal metallic bars a a b b c cd d upon the upperpart of the switch-board S, as shown in the ligures. These bars are insulated from each other and are placed, preferably, above the spring-jacks, as shown in the drawing. They are arranged in pairs, each pair, as a a', being connected by wires with one of another series of springjacks, j', j, j?, and j, mounted upon an operators table, B, separate from the switch-board S, which may be placed in any convenient part ofthe same room. Thus the bar a is connected with one side ofthe 'spring-jack j by a Wire, which also passes through a visual signal or annunciator, fr. This signal is actuated by an electromagnet in a well-known manner whenever the magnet is traversed by an electric current. The other side of the springjack is connected directly with the bar a by areturnwire, as shown. Thus each one of the springjaoks uponthetableBisincluded,together with its annunciator, in a loop-conductor, the terminals of which are formed by one of the pairs of bars upon the switchboard.

Upon or beside the operators table B is placed an apparat-us for the use of the operator in receiving and transmitting calls,signals, or alarms, which may consist of a magneto-genen ator operated by a crank, k, and a bell, r, actu-u ated hy an electromagnet. A telephone trans* mitter and receiver, t, titted with the usual switch, automatic or otherwise, for throwing either the signaling or the speaking apparatus` into the circuit at pleasure, is also provided. This apparatus is placed in a looped wire or circuit, one leg, 71, of which terminates in one side ofa double-faced terminal wedge, U, while the other leg, h', goes to the lever of a switch, s, on the operatorstable B. When the switch s is moved to the right, it completes the loop th rough the wire h to the remaining side ofthe wedge U; but when turned to the left, as shown in the figure, which is its normal position, it connects the leg h of the loop directly to the earth at G.

Upon the same switch -board S, with the spring-jacks below the annuneiators,are placed a number of parallel metallic conducting bars or strips, ZZvl m. The bar m is. connected by means of a wire, 15,with'asignal-transmitting apparatus, M, which is preferably kept constantly in operation. I have shown an ordinary magnetogenerator which may be rotated by a crank, in', turned by hand,or, preferably, by power. As the other terminal of its coils is connected to the earth at G', its action is to transmit a series of rapid, alternate, positive, and negative impulses through any conductor which is made to form a connection between theinsulated bar m and the earth. The func- The manner in which my improved System is operated will be understood from the following explanation: At the central station one attendant is stationed at the switch S, who is termed the switchmam and one at the disconnectingtablawhois termed an operatorJ Where the number of lines is very great, additional switchmen and operators may be employed, as required. lf now the sub-station upon line 1 desires to be connected with the sub-station upon line 9, for example, the subscriber at that point transmits an electrical impulse by means of his signaling apparatus to the central station,which actuates the visual signal A and then passes directly to the earth at G. The switchman at the central station at once takes a liexible conductor, (),aud inserts its terminal N into the springjack J, which disconnects the linewire l from the annunci ator and the earth, as hercinbefore explained, and places it in connection with the metallic peg P atthe other end of the flexible conductor. He next touches thc peg P to the bar m, which completes the circuit through the wire 15 and signal-transmitter M to the earth at G', which operation causes the pulsations which are con stantly being sent out from the transmitter to pass over the line to substation and actuate the alarm or signal at that point in response to the call which has previously been sent in. The switchmantakesthesame pegPandinserts it with a twisting motion into a hole'in one of the bars Z or Z, which operation puts the operator at the telephone T into direct communication with the sub-station. The operator converses with the subscriber and ascertains that he wishes to be connected with number 9. He then calls out or hands a ticket to thc switchman ,with the two numbers (as l and 9) written on it, who upon receiving it immediately completes the connection by changing the peg l? from the bar Z or Z to the bar a. The switchrman theu,taking another {lexible conductor precisely similar to O with its wedge terminal and peg, inserts the pin in the bar a' and Vtouches the wedge-block to the bar m. This places the spring-jack j at table B in circuit with the callvgenerator M, and causes the annunciator r to drop, and then the switchman immediately plugs the switch to the spring-jack J9, which connects the lines of the two subscribers. The operator at the table,

IOO

. mediate operator.

having his attention thus called, inserts his telephone t and signaling apparatusk into the.

united circuit by Aplacing wedge U in the spring-j ack j', and calls up the second sub-station on line 9 and-puts the two in correspondence. He then restores the annunciator to its normal position, in which it is ready to act as a disconnecting-signal. vWhen the-two subscribers have finished their conversation, they announce the fact by sending an impu-lse from one substation or the other, which actuates the visual signal r', whereupon the switchman is notified by the table-operator to disconnect the united lines and restore them to their normal relations.

The number of pairs of connecting-bars, as a a b b', Src., that will be required, will depend upon the number of lines entering the :exchange and the proportion of them which will ordinarily require to be coupled to either at any one time, and the same is true of the number of telephones T T and their attachments. The object of the arrangements which lhave been described is, generally speakinggtoh subdivide the labor of answering calls, connecting and disconnecting lines, &c., among a number of diiferent attendants, so that the service may be rendered as expeditious as possible where a very large number of lines are assembled together. Thus under the organization described the table-operator calls the subscriber wanted, puts the calling-subscriber in connection with him, and removes his plug U, so as to be ready for the next call while the two last connected arc still talking. When notified by the falling of the annunciator-drop that they are through talking, he notifies the switchman to disconnect, and re'- places his annunciatordrop ready for the next signal. Under the organization shown the annunciator thus serves both to notify the table-operator of connections to be made on his table, and also acts as a disconnecting-signal.

I have described as part of the above open. ation the putting of an operator at the telephone Tinto communication with a callingsubscriber, who directs the switchman to make the necessary connections with thetable-operator, but in practice I frequently dispensed with this intermediate operator, the switchman, when the call came in, making the connection directly with the table-operator who conversed with the subscriber, ascertained and called np the party wanted, and made the necessary connections, as above described, thus dispensing with the services of an inter- Under this method of operation the circuitconnections were as follows: Beginning at the ground G', through battery or generator M, wire 15, bar m, face n, plug N, flexible cord O, plug P, loop-strap d', annunciator r, base of l spring-jack jt, double-faced plug U, through its cord and wire into magneto-machine le,

thence by Wire h and three-point switch s back to ground G. When a signal came in over one ofthe lines, say No. 1, the switchrnan took the round plug P and inserted vit in the strap cl of the switch-board, and then touched theconducting-face n of the flat plug at the other end of the conducting-cord Oupon the. strap m, which caused the annunciator r4 on the operators table to drop, thus calling the y spring-jack jt, and thev three-point switch s' ,f was upon the ground connection. The switchman then withdrew his plug from contact with the strap m and inserted it under the springjack J', with the insulated face down. The table-operator then moved the switch fr of the magneto-machine to the right, put the handtelephone to the ear, and spoke through the other telephone to the subscriber. Ascertaining from the subscriber on line 1 the party with whom he wished to make connection, the table-operator gave the twonumbers to the switchman on a ticket. He then, taking another pair of plugs united by a exible cord, inserted the flat plug under thesprng-jack J5 'of the second line and inserted the round plug linthe upper strap, d, of the pair of loop-straps already used. The table-.operator then turn ed the three-point switch s to the right, thus cutting off the ground and placing the telephones and magneto by a loop in the circuit between the two subscribers. He then rang his magneto-bell, notifying both parties that the connection yhad been made, and talked with either of them if necessary. Finding all right he pulled the double plug out from the springjack and left the parties to themselves. When IOO rang down the annunciator'ia4 between them. 1

The operator then, by ticket, directedv the switchman to draw the plugs from thespring-v jacks and loop-straps at the switch-board. 'As soon as the double plug was withdrawn from the spring-jack it was inserted in the one next on the right and the switch-connections restored to their normal condition for the proper reception of another signal. The switchman also habitually used the pair ot' straps next above those first used, which corresponded with the ones in which the operator had inserted the plug, so that everythingwas in readiness for the next signal.

I disclaim in this applicationlthe subjectmatter claimed in my respective applications No. 11,389, filed June 9, 1880,'patentediAugust'14, 1884, as No. 303,714, and Nor-11,759, tiled June 12, 1880, limiting the claim in' this IZO application to thespecific subject-matter set' fore-set forth, -of a series of subscribers lines;

In testimony whereof I have hereunto subscribed my name this 5th dayof March, A. D. 1o 1884.

HORACE HAMLINE ELDRED.

Witnesses:

PHILU? S. STONE', V. M. BERTHOLD. 

